Hydrostatic wave energy conversion system

ABSTRACT

A system for conversion of hydrostatic pressure variations of sea waves into useful energy is disclosed. The system is comprised of a sealed casing ( 12 ) with a membrane-like cover ( 16 ). The cover operates piston ( 52 ) under the pressure of the waves. The piston compresses air into vessel ( 22 ), from which it is discharged ( 86 ) to drive turbine ( 24 ) and produce electric energy ( 26 ). The piston ( 52 ) is recoiled back upwards by second piston ( 56 ), reciprocable within cylinder  58.  The effective volume of the cylinder  58  is variable for counter-pressure adjustment purposes.

BACKGROUND OF THE INVENTION

The present invention relates to systems for converting the energy ofsea waves into useful energy.

Most of the state-of-the-art systems proposed and developed for theobjective in question were designed for the exploitation of the kineticenergy of sea surf waves; all of these have failed due to technical andother reasons.

It is the object of the present invention to provide an off-shore,submerged energy generator utilizing the differential hydrostaticpressure prevailing between peaks and valleys of sea waves.

It is a further object of the invention that the generator beself-contained, i.e. working in closed cycles, without any externalintervention, servicing, controls, etc.

SUMMARY OF THE INVENTION

Thus provided according to the present invention there is a system forthe conversion of hydrostatic pressure variations such as generated byoff-shore sea waves, into useful energy, comprising a casinghermetically sealed and submerged in the sea underneath the waves level,at least one wall of the casing being adapted to become displacedinwards and outwards of the casing under variable hydrostatic pressureapplied thereon, a cylinder-and-piston system, (“the first system”) thepiston being coupled to the said one wall to move in unison therewith,valve means associated with the first system so that on every stroke ofthe piston a quantity of a fluid supplied to the cylinder is compressedout of the cylinder into a pressurized fluid vessel and means forconverting the energy of the pressurized fluid stored in the pressurizedfluid vessel into useful energy.

Preferably the system further comprises a second cylinder-and-pistonsystem (“the second system”), the piston thereof being coupled to thepiston of the first system to move in unison therewith and means forcontrollably varying the effective volume of the cylinder of the secondsystem.

The effective volume varying means may comprise a source of a liquid andmeans for introducing/evacuating the liquid into/from the said cylinder.

Further means may be provided for increasing the initial pressure in thesaid effective volume space.

BRIEF DESCRIPTION OF THE DRAWINGS

These and additional objects, advantages and constructional features ofthe invention will become more clearly understood in the light of theensuing description of a preferred embodiment thereof, given by way ofexample only, with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic view illustrating the underwater working locationof the system and some of its sub-systems; and

FIG. 2 is a schematic representation of the system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Shown in FIG. 1 is a portion of a sea body of water, between bottom Aand surface B, waves C, forming peaks C1 and valleys C2. It is thedeferential hydrostatic pressure prevailing near the bottom A (oranywhere else below the surface B), namely the head balance (H1-H2) thatis harnessed to produce useful energy according to the principles to beexplained below.

The energy generator generally denoted 10, is comprised of abarrel-shaped casing 12, with circular side wall 12 a, bottom 12 b andcover 14.

The generator 10 is self-contained in the sense that it works in aclosed loop and need not to cooperate with any other system; thefunctions of certain sub-systems are automatically controlled byfeedback from relating other sub-systems, as will be seen later on. Thisstand-alone feature of the generator is regarded as one of the uniquesof the present invention.

Furthermore, the generator 10 need not to rest on the sea bottom A, butcan be held in buoyancy thereabove using suitable anchoring means (notshown).

As further schematically seen in FIG. 1 the cover 14 of the casing 12 ismade as a membrane 16, namely a rigid plate connected to the side wall12 a of the casing 12 intermediate a yeildable sheet 16 a, thus allowingthe displacement of the plate 16 a up and down following changes in thedifferential pressures applied thereto (between the interior and theouter pressures as will be explained in detail below).

The general sub-systems of the generator 10 will be now identified forbetter understanding of the more detailed description given inconjunction with FIG. 2; these include:

First cylinder-and-piston assembly or system 18;

Second cylinder-and-piston system 20;

Pressurized fluid (air) accumulating vessel 22;

Turbine 24 drivingly coupled to electrical power generator 26;

Liquid supply source 28 for varying the volume of the cylinder of system20; and

Interim fluid (air) supply vessel 30, for supplying the cylinder ofsystem 18, and connected via conduit 32 to turbine 24 discharge port,thus closing the working loop of the fluid.

Referring now for more details to FIG. 2, it should be first noted thatin order to function properly, the pressure prevailing within the casing12 of the generator 10, denoted Pg, must always be kept less than theminimum hydrostatic pressure applied by the waves B. namely under thewater head H2; otherwise, the membrane cover 16 will not respond to thedifferential pressure (H1-H2), i.e. become displaced up and down asdesired.

Therefore, outer pressure gauge 40 and inner pressure gauge 42 areprovided for constantly measuring these pressures, and to govern theoperation of an electrically operated, reversible suction pump 44 forlowering the internal pressure; relief valve 46 is associated with thehigh pressure vessel 22 for increasing the internal pressure, as thecase may be.

A central computerized unit CPU is included, which controls the variousoperational parameters of the generator sub-systems as will be explainedbelow.

The first cylinder-and-piston system 18 comprises cylinder 50 and piston52 with piston rod 54, which extends upwards where it is rigidlyconnected to the plate 16, as well as downwards out of the cylinder 50,where it becomes the rod of piston 56 of the second cylinder-and-pistonsystem 20, provided with cylinder 58. Thus defined are upper and lowereffective spaces denoted S1 and S2.

The system 18 acts as a double-stroke air pump, compressing air suppliedfrom vessel 30 to vessel 22. There are provided two unidirectionalinlets 60, 62 connected to the vessel 30 on the one hand, and twounidirectional outlets 64, 66, leading to the vessel 22, as shown.Reciprocation of the piston 52 in either direction will thereforepressurize air into the vessel 22.

Referring to the second cylinder-and-piston system 20, it will be notedthat the stroke of the piston 52 is opposed by that of the piston 56,both being mounted to a common rod 54.

The cylinder 58 is of a variable effective volume (space S3), achievedby filling it partly, to a controlled amount, with liquid 70, such asoil, through pump 72 from container 28.

The variable space S3 within the cylinder 58 underneath the piston 56 isalso adapted to be charged with pre-determined, variable pressure to besupplied from pressurized air vessel 22 via control valve 80 andpressure regulator 82.

The turbine (or air motor) 24 is operated by the pressurized air storedin vessel 22, via control valve 84 and pressure regulator 86.

As already explained, the discharge port of the turbine 24 is connectedby conduit 32 and control valve 88 to the interim air supply vessel 30.

Finally, a rechargeable battery 90 recharged by the generator 26(through voltage regulator 92) is included for supplying electric powerto operate the CPU, the suction pump 44, the oil pump 72 and all thecontrol valves and other devices as apparent from the foregoingdescription.

The operation of the generator 10 proceeds as follows. As alreadymentioned, the internal pressures Pg is pre-set and maintained to avalue less to a certain extent, than the value of the externalhydrostatic pressure to which the membrane cover 16 is subjected.Otherwise, should the internal pressure exceed the external pressure,the membrane cover would not respond to, i.e. become displaced downwardsunder the external pressure represented by the water head H1; and if theinternal pressure is too low, again the membrane 16 will not function,but remain stationary at its lowermost position, irrespective of areduced water head H2.

Regulation of the pressures is maintained by the suction pump 44, or therelief valve 46 (controlled by pressure gauges 40, 42), in accordancewith the actual working conditions, taking into account, among otherparameters, the height of the sea waves B at any given time.

Supposing that the internal pressure has been properly adjusted, thepiston 52 is at its uppermost position, and the generator is firstsubjected to the increased hydrostatic pressure proportional to a wavepeak C1, then, under such elevated pressure the membrane cover 10 willdescend. The piston will move down and a quantity of air (space S2) willbe compressed into the vessel 22.

Simultaneously, a pressure will be built-up in the space S3. Thiscounter-pressure is essential in order to achieve the upwards stroke ofthe piston 52 along with the lifting of the membrane cover 16, after thewave peak C1 has passed away and a lower hydrostatic pressure, relatedto head H2, prevails.

The appropriate adjustment of the counter pressure, which is of majorimportance for starting and maintaining the cyclic operation of theunit, is achieved by adjusting at least one of the following variants:Changing the effective volume S3, and/or charging extra pressurethereinto. The first variant is accomplished in the present example bythe filling/evacuating the oil 70 into/out of the lower part of thecylinder 58; and the second variant is adjusted by partly directingcompressed air from the vessel 22, though pressure regulated valve 82into the space S3.

The combination of the two variants, each being individuallycontrollable by the CPU, along with suitable calculation of the area ofthe piston 56 relative to that of the piston 52 ensure the availabilityof a wide range of changeable factors required for achieving the desiredresult, namely, effectively, lifting the piston 56 when a relativerelief of force is sensed by the membrane 16, caused by the decreasedhydrostatic pressure H2, with minimum loss of energy.

As the compression cycles continue, the pressure will be built-up withinthe vessel 22. Upon reaching a level sufficiently high, pressureregulator 86, by a command of the CPU, will open and the compressed airwill drive the turbine 24 for as long as the pressure remains effectivefor that purpose. Again controlled by the CPU, the valve 84 will closeand a new cycle will be started.

Low pressure air is directed through conduit 32 from the outlet port ofthe turbine 24 to the vessel 30, and therefrom to the cylinder 50. Theair is therefore recycled in a closed working loop (except for a portioneither expelled from the relief valve 46, or sucked by suction pump44—as already mentioned above).

It goes without saying that a plurality of generators as hereindescribed, are readily adapted to work in parallel, thus compensatingfor the inherent operating pauses of each one of them.

Once installed, no maintenance or servicing is requested for a longperiod (say, for replacing the batteries 90). It is thus suitable foruse along coasts of deserted areas, where the supply of conventionallyproduced electricity is too expensive.

Those skilled in the art will readily understand that various changes,modifications and variations may be applied to the invention as aboveexemplified without departing from the scope of the invention as definedin and by the appended claims.

What is claimed is:
 1. A system for conversion of hydrostatic pressurevariations generated by off-shore sea waves, into useful energy,comprising: a casing hermetically sealed and submerged in the seaunderneath the waves level; means for generating a sub-pressure withinthe casing; at least one wall of the casing being adapted to becomedisplaced inwards and outwards of the casing under variable hydrostaticpressure applied thereon; a first cylinder-and-piston system having apiston coupled to the said one wall to move in unison therewith; valvemeans associated with the first system so that on every stroke of thepiston a quantity of a fluid supplied to the cylinder of the firstsystem is compressed out of the cylinder into a pressurized fluidvessel; a second cylinder-and-piston system having a piston rigidlycoupled to the piston of the first system to move in unison therewith;means for controllably varying the effective volume of the cylinder ofthe second system in relation with the force applied by said one wall onthe piston of the first system; and means for converting the energy ofthe pressurized fluid stored in the pressurized fluid vessel into usefulenergy.
 2. The system of claim 1 wherein the volume varying meanscomprise a source of a liquid and means for introducing/evacuating theliquid into/from the cylinder of the second system.
 3. The system ofclaim 2 wherein means are provided for controlling theintroduction/evacuation of the liquid as a function of hydrostaticpressure variations.
 4. The system of claim 3 wherein said source ofliquid comprise a reservoir of the liquid in communication with thecylinder of the second system, and said liquid introduction/evacuationmeans comprises an electric reversible pump controlling the flow of theliquid into/from said cylinder of said second system.
 5. The system ofclaim 1 wherein said means for controllably varying the effective volumeof the cylinder of said second system comprising means for increasingthe initial pressure in the said effective volume.
 6. The system ofclaim 5 wherein the increased pressure is supplied from the pressurizedfluid vessel.
 7. The system of claim 1 wherein the energy convertingmeans comprise a turbine drivingly coupled to an electric generator. 8.The system of claim 7 further comprising conduit means connected betweenthe outlet of the turbine and the inlet of the cylinder of the firstsystem.
 9. The system of claim 8 wherein said means for generating asub-pressure within said casing comprising fluid suction means forlowering the pressure prevailing within the casing.
 10. The system ofclaim 9 wherein said means for generating a sub-pressure within saidcasing comprising means for increasing the pressure prevailing withintie casing.
 11. The system of claim 10 further comprising means formeasuring the pressure prevailing within the casing, and means forcontrolling the pressure by setting into operation one or the other ofthe fluid suction means or the pressure increasing means.
 12. The systemof claim 11 comprising computerized control means for operating said oneor the other means, for adjusting the pressure within the casingrelative to a pre-determined pressure.
 13. The system of claim 12wherein the pre-determined pressure is set as a function the hydrostaticpressure to which the casing is subjected.
 14. The system of claim 13comprising an electric rechargeable battery supplied by the electricgenerator.